1 files changed, 48 insertions, 0 deletions

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+--- lam.list
+
+local list = {}
+local util = require "util"
+local types = require "types"
+table.unpack = table.unpack or unpack
+
+list.Null = setmetatable({}, {
+                __type = "Null",
+                __tostring = function(self) return "()" end,
+})
+
+list.isNull =
+        function (x)
+                return x == list.Null
+        end
+
+list.List =
+        function (tbl)
+                local function tolist (base, items)
+                        if #items == 0 then return base end
+                        return tolist (
+                                types.Cons(table.remove(items), base),
+                                items
+                        )
+                end
+                return tolist(list.Null, tbl)
+        end
+
+list.isList =
+        function (x)
+                if list.isNull(x) then
+                        return true
+                elseif types.isa(x, "Pair") then
+                        return list.isList(x[2])
+                else
+                        return false
+                end
+        end
+
+list.fold1 =
+        function (fn, seed, lis)
+                if list.isNull(lis) then return seed end
+                return list.fold1(fn, fn(seed, lis[1]), lis[2])
+        end
+
+---
+return list